Growth hormone (GH) dose, but not exon 3-deleted/full-length GH receptor polymorphism genotypes, influences growth response to two-year GH Therapy in Short Small-for-Gestational-Age Children.

CONTEXT: In short small-for-gestational-age (SGA) patients, the exon 3-deleted(d3)/full-length (fl)-GHR polymorphism was associated with responsiveness to GH therapy (30-48 microg/kg.d); however, these results were not confirmed for higher GH doses (56-66 microg/kg.d). We hypothesized that higher doses would mask the lower dose differences. OBJECTIVE: Our objective was to evaluate, in short SGA patients, 2-yr growth response to GH therapy (32.1 +/- 3.8 microg/kg.d) according to exon d3/fl-GHR genotypes. SETTING: This was a 2-yr follow-up study. PATIENTS: There was a total of 60 short SGA children (d3/d3 n = 8, d3/fl n = 23, and fl/fl n = 29). There were 11 children that entered puberty during the second follow-up year. Results were evaluated for all patients (group A1, n = 60, 7.7 +/- 2.7 yr) and for patients who remained prepubertal (group A2, n = 49, 6.9 +/- 2.2 yr). MAIN OUTCOME MEASURES: Patients were followed by a single clinical team, and exon d3/fl-GHR genotypes were determined and analyzed in the same hospital. RESULTS: In groups A1 and A2, growth velocity significantly (P < 0.0001) increased during the first and second years of therapy, as did height sd score (SDS). These increases were similar in each exon d3/fl-GHR genotype. Total 2-yr height gain (cm, SDS) did not differ statistically among genotypes: group A1, 15.0 +/- 2.0 cm and 1.15 +/- 0.45 SDS in d3/d3, 16.0 +/- 2.4 cm and 1.17 +/- 0.51 SDS in d3/fl, 16.1 +/- 2.4 cm and 1.15 +/- 0.53 SDS in fl/fl; and group A2, 15.4 +/- 2.0 cm and 1.03 +/- 0.42 SDS in d3/d3, 15.6 +/- 2.1 cm and 1.22 +/- 0.51 in d3/fl, and 16.2 +/- 2.6 cm and 1.21 +/- 0.56 SDS in fl/fl. CONCLUSIONS: These results did not confirm our hypothesis and show that, in short SGA children, 2-yr growth response to GH therapy 32.1 +/- 3.8 microg/kg.d was similar for each exon d3/fl-GHR genotype carried, as occurred in our previous study using 66 microkg.d.